Previously, many types of tilters have been used to provide an effective means for producing the required rotational movement to open and close the slats of a horizontal or venetian blind.
In some prior art the slats are partially revolved by a tilter which employs a worm gear that is manually actuated by a rotatable wand, wherein the operator twists the wand the desired direction and the movement is transmitted via an endless screw at right angles to a spur-like gear.
Other developments in the art of horizontal blinds employs a pulley, drum or irregular shaped tilt roll on which a pair of cords or lines are attached. By pulling one or the other line, the actuator rotates the tilt rod proportionally to the line linear movement.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however the following U.S. patents are considered related:
______________________________________ Pat. No. INVENTOR ISSUED ______________________________________ 5,341,865 Fraser et al 30 August 1994 5,297,608 Rap et al 29 March 1994 4,821,789 Van Rens 18 April 1989 4,676,292 Valle et al 30 June 1987 4,541,468 Anderson 17 September 1985 4,487,243 Debs 11 December 1984 4,352,385 Vecchiarelli 5 October 1982 4,141,402 Marotto 27 February 1979 ______________________________________
U.S. Pat. No. 5,341,865 issued to Fraser et al, teaches a tilt roll mechanism with an asymmetrical cross section and includes bearings on a support to connect flexible cords of ladder laces that extend around the body. Control means are accomplished using a worm gear engaging a pinion with appropriate number of teeth on the worm gear to prevent overtilting.
Rap, et al in U.S. Pat. No. 5,297,608 discloses a tilter mechanism for a venetian blind that employs a fixed hollow drum secured to a headrail and a hollow rotatory mechanism that is positioned in the drum. A tilt cord is wound around the pulley and, when pulled downward, tilts the entire headrail thereby tilting the attached slats.
U.S. Pat. No. 4,821,789 issued to Van Rens is for a tilt drum which secures the upper ends of a cord ladder.
Valle et al in U.S. Pat. No. 4,676,292 teaches a tilter mechanism that uses a spur gear with a smooth peripheral portion having no teeth, and a worm gear that engages the teeth for rotation by a wand.
Anderson in U.S. Pat. No. 4,541,468 also teaches a worm gear that rotatably meshes into engagement with a worm wheel. The wheel has some teeth having a lesser height such that the gear may slip over the shortened teeth to act as a slip clutch.
U.S. Pat. No. 4,487,243 of Debs has a plastic housing open at the top through which a gear and worm shaft are introduced before closing the cover.
Vecchiarelli's U.S. Pat. No. 4,352,385 is for a tilter mechanism employing a worm and wormwheel.
Finally U.S. Pat. No. 4,141,402 of Marotto discloses a tilter operating mechanism that uses a stub shaft that depends from a head rail with a cross piece on a lower stub shaft attaches to a wand.